Q.1 Which of the following is a passive method of braking used in electric drives?
Dynamic braking
Regenerative braking
Electromagnetic braking
Mechanical braking
Explanation - Mechanical braking uses physical friction elements such as brakes pads or discs and does not rely on electrical components.
Correct answer is: Mechanical braking
Q.2 In dynamic braking, the motor acts as a generator to provide braking torque. What happens to the generated electrical energy?
It is returned to the power supply.
It is dissipated as heat in the motor windings.
It powers auxiliary loads.
It is stored in a battery.
Explanation - Dynamic braking converts kinetic energy into heat in the windings, not feeding it back to the supply.
Correct answer is: It is dissipated as heat in the motor windings.
Q.3 Regenerative braking in an electric drive system primarily serves to:
Increase braking torque by using magnetic fields.
Return energy to the power source or storage.
Reduce noise during braking.
Heat the motor for cooling.
Explanation - Regenerative braking captures kinetic energy and feeds it back into the supply or storage, improving efficiency.
Correct answer is: Return energy to the power source or storage.
Q.4 Which braking method requires a separate circuit to dissipate the generated current?
Dynamic braking
Regenerative braking
Electromagnetic braking
Mechanical braking
Explanation - Dynamic braking needs a resistive path or circuit to safely dissipate the generated energy as heat.
Correct answer is: Dynamic braking
Q.5 The main advantage of regenerative braking over dynamic braking is:
Lower maintenance cost.
Higher braking torque.
Energy recovery.
Simpler design.
Explanation - Regenerative braking recovers electrical energy, improving overall efficiency, unlike dynamic braking which wastes it as heat.
Correct answer is: Energy recovery.
Q.6 Which of these is NOT a typical application of regenerative braking?
Electric railways
Hybrid automobiles
Heavy freight trucks
Static load elevators
Explanation - Static elevators do not involve moving heavy loads that can benefit from regenerative energy capture.
Correct answer is: Static load elevators
Q.7 What is the primary limitation of dynamic braking in high-speed drives?
Insufficient braking torque at high speeds.
Excessive heating of the brake circuit.
Difficulty in controlling the braking torque.
High initial cost.
Explanation - Dynamic braking dissipates large amounts of energy as heat, which can lead to overheating at high speeds.
Correct answer is: Excessive heating of the brake circuit.
Q.8 During regenerative braking, the voltage at the motor terminals typically:
Drops below the supply voltage.
Equals the supply voltage.
Rises above the supply voltage.
Stays constant.
Explanation - The motor generates a higher voltage than the supply when braking and feeding energy back.
Correct answer is: Rises above the supply voltage.
Q.9 Which braking method is most suitable for an electric vehicle with a large battery bank?
Dynamic braking
Regenerative braking
Mechanical braking
All of the above
Explanation - Large battery banks allow energy to be stored during regenerative braking, maximizing efficiency.
Correct answer is: Regenerative braking
Q.10 Electromagnetic braking uses:
Permanent magnets only.
Induced currents in conductive discs.
Resistive elements in the motor.
Mechanical friction.
Explanation - Electromagnetic brakes generate eddy currents in conductive plates, creating opposing magnetic fields.
Correct answer is: Induced currents in conductive discs.
Q.11 What is the main drawback of using electromagnetic brakes in high-speed applications?
They are heavy.
They require cooling.
They cause wear on magnets.
They are expensive.
Explanation - Eddy currents generate heat in the plates, necessitating active cooling at high speeds.
Correct answer is: They require cooling.
Q.12 Which control strategy is commonly used to blend dynamic and regenerative braking?
PWM switching
Phase-locked loop
Vector control
Open-loop control
Explanation - Vector control allows precise torque and speed regulation, facilitating smooth blending of braking modes.
Correct answer is: Vector control
Q.13 In a regenerative braking system, the maximum recoverable energy is limited by:
The motor's inductance.
The supply voltage.
The battery's voltage ceiling.
The gearbox efficiency.
Explanation - The battery cannot accept voltage beyond its rated maximum; thus energy recovery is capped.
Correct answer is: The battery's voltage ceiling.
Q.14 Which of the following is a primary reason to use mechanical brakes in addition to electrical braking?
To provide continuous braking.
To reduce electrical noise.
To provide redundancy.
To improve regenerative efficiency.
Explanation - Mechanical brakes act as a backup in case of failure in the electrical braking system.
Correct answer is: To provide redundancy.
Q.15 Which braking method best prevents rotor slip during emergency stops?
Dynamic braking
Regenerative braking
Electromagnetic braking
Mechanical braking
Explanation - Mechanical brakes directly clamp the shaft, preventing slip regardless of motor slip conditions.
Correct answer is: Mechanical braking
Q.16 The braking torque in dynamic braking is proportional to:
Rotor speed only.
Rotor speed and current.
Voltage only.
Magnetic flux.
Explanation - Torque ∝ speed × induced EMF, which depends on speed and current.
Correct answer is: Rotor speed and current.
Q.17 Which parameter is NOT directly affected by regenerative braking?
Motor temperature
Supply voltage
Mechanical shaft speed
Windings resistance
Explanation - Windings resistance remains constant; regenerative braking affects current, voltage, and speed.
Correct answer is: Windings resistance
Q.18 Which of the following devices is commonly used to dissipate heat generated in dynamic braking resistors?
Thermocouple
Heat sink
Capacitor
Inductor
Explanation - Heat sinks increase surface area for effective thermal dissipation.
Correct answer is: Heat sink
Q.19 During regenerative braking, the inverter must:
Switch to DC mode.
Provide a reverse voltage to the motor.
Short the motor windings.
Disable the motor controller.
Explanation - To feed power back, the inverter supplies a voltage opposite to the normal drive direction.
Correct answer is: Provide a reverse voltage to the motor.
Q.20 Which of these is a typical characteristic of an eddy-current brake?
High wear rate.
High energy consumption.
No moving parts.
Requires lubrication.
Explanation - Eddy-current brakes rely on induced currents in conductive plates, having no mechanical contact.
Correct answer is: No moving parts.
Q.21 In electric drives, the term 'braking torque' refers to:
Torque used for acceleration.
Torque that opposes rotation.
Maximum rated torque.
Torque produced by the gearbox.
Explanation - Braking torque resists motion, slowing the motor or load.
Correct answer is: Torque that opposes rotation.
Q.22 Which braking method uses a 'short-circuit' of the motor windings to dissipate energy?
Dynamic braking
Regenerative braking
Electromagnetic braking
Mechanical braking
Explanation - Short-circuiting the windings creates high currents that convert kinetic energy into heat.
Correct answer is: Dynamic braking
Q.23 In regenerative braking, the current flowing back to the supply is known as:
Regenerative current
Inversing current
Feedback current
Brake current
Explanation - This current is directed back into the power network during braking.
Correct answer is: Regenerative current
Q.24 Which of the following is a safety consideration when using regenerative braking?
Over-voltage protection.
High current filtering.
Mechanical wear monitoring.
All of the above.
Explanation - Regenerative braking can produce high voltages and currents; safety systems must guard against them.
Correct answer is: All of the above.
Q.25 Which braking strategy is most energy-efficient for a hybrid electric vehicle?
Dynamic braking only.
Regenerative braking only.
Hybrid of regenerative and dynamic braking.
Mechanical braking only.
Explanation - Combining both methods maximizes energy recovery while ensuring sufficient braking torque.
Correct answer is: Hybrid of regenerative and dynamic braking.
Q.26 What is the typical maximum speed limit for effective dynamic braking in industrial drives?
10-20 rpm
200-400 rpm
2000-4000 rpm
10,000-20,000 rpm
Explanation - Beyond this range, heat generation becomes excessive and efficiency drops.
Correct answer is: 2000-4000 rpm
Q.27 Which component is essential for controlling the amount of current during dynamic braking?
Brake resistor
Motor controller
Gearbox
Cooling fan
Explanation - The resistor limits current flow and manages heat dissipation during braking.
Correct answer is: Brake resistor
Q.28 In a regenerative braking system, the power electronics typically use which topology?
Half-bridge inverter
Full-bridge inverter
Three-phase bridge inverter
Single-phase inverter
Explanation - Three-phase inverters provide balanced power flow for regenerative operation.
Correct answer is: Three-phase bridge inverter
Q.29 Which of the following best describes the torque-speed characteristic of regenerative braking?
Torque increases with speed.
Torque is constant.
Torque decreases with speed.
Torque is independent of speed.
Explanation - Higher speeds generate larger back-EMF and more recoverable torque.
Correct answer is: Torque increases with speed.
Q.30 Which braking method is most appropriate for a low-speed conveyor belt system?
Dynamic braking
Regenerative braking
Mechanical braking
Electromagnetic braking
Explanation - Low speeds render electrical braking inefficient; mechanical brakes are simpler and effective.
Correct answer is: Mechanical braking
Q.31 The main purpose of a brake controller in a regenerative drive system is to:
Switch the motor from drive to brake mode.
Monitor battery voltage.
Control motor speed.
Measure rotor position.
Explanation - A controller manages the transition between driving and braking modes.
Correct answer is: Switch the motor from drive to brake mode.
Q.32 What is the primary failure mode of dynamic braking resistors?
Overheating and melting.
Short circuits.
Open circuits.
Mechanical wear.
Explanation - Resistors are exposed to high power dissipation and can fail due to thermal degradation.
Correct answer is: Overheating and melting.
Q.33 Which type of motor is most commonly used for regenerative braking in electric vehicles?
DC shunt motor
Induction motor
Brushed DC motor
Permanent magnet synchronous motor
Explanation - PMSMs provide high efficiency and controllable torque for regenerative operation.
Correct answer is: Permanent magnet synchronous motor
Q.34 Which control parameter is critical to prevent overvoltage during regenerative braking?
Current limit
Voltage limit
Torque limit
Speed limit
Explanation - The inverter must ensure the output voltage stays within safe boundaries to protect equipment.
Correct answer is: Voltage limit
Q.35 During dynamic braking, the motor acts as a:
Generator
Motor
Transformer
Switch
Explanation - The rotating magnetic field induces currents that generate heat in the resistive load.
Correct answer is: Generator
Q.36 Which of the following is a disadvantage of mechanical braking?
High wear and maintenance.
Inability to provide braking torque.
Complex control logic.
High energy consumption.
Explanation - Friction elements wear out and require regular replacement.
Correct answer is: High wear and maintenance.
Q.37 Which braking method is typically used in a large freight train to recover braking energy?
Dynamic braking
Regenerative braking
Electromagnetic braking
All of the above
Explanation - Freight trains employ a combination of braking strategies to maximize energy efficiency.
Correct answer is: All of the above
Q.38 In a dynamic braking resistor, the resistance value:
Must be fixed.
Can be adjusted by the controller.
Is irrelevant.
Is always low.
Explanation - Variable resistors allow optimal heat dissipation based on braking demand.
Correct answer is: Can be adjusted by the controller.
Q.39 The braking torque produced by a regenerative brake is:
Proportional to current.
Inversely proportional to voltage.
Proportional to speed.
Independent of speed.
Explanation - Higher speed yields higher back-EMF and thus more regenerative torque.
Correct answer is: Proportional to speed.
Q.40 Which component is used to isolate the brake resistor from the main circuit during non-braking periods?
Switch
Diode
Relay
Capacitor
Explanation - A relay can quickly connect or disconnect the resistor from the circuit.
Correct answer is: Relay
Q.41 What is the main reason for using a 'soft start' in dynamic braking circuits?
Reduce inrush current.
Improve braking torque.
Increase energy recovery.
Prevent electromagnetic interference.
Explanation - Soft start limits the sudden surge of current when the brake is engaged.
Correct answer is: Reduce inrush current.
Q.42 In regenerative braking, the power returned to the supply is typically in the form of:
Mechanical energy.
Electrical energy.
Chemical energy.
Thermal energy.
Explanation - The motor generates electrical power that is fed back to the supply or storage.
Correct answer is: Electrical energy.
Q.43 Which of the following is a typical application of electromagnetic brakes?
Elevator systems
Bicycle brakes
Wind turbines
Electric car brakes
Explanation - Elevators often use electromagnetic brakes due to their reliability and low maintenance.
Correct answer is: Elevator systems
Q.44 The braking torque in mechanical brakes is mainly affected by:
Brake pad material.
Motor speed.
Battery voltage.
Gear ratio.
Explanation - Friction coefficient of pads determines the torque generated.
Correct answer is: Brake pad material.
Q.45 Which braking method can cause a sudden increase in motor temperature due to rapid energy dissipation?
Dynamic braking
Regenerative braking
Mechanical braking
All of the above
Explanation - Dynamic braking dissipates energy as heat in resistors, raising temperatures quickly.
Correct answer is: Dynamic braking
Q.46 In which scenario is regenerative braking NOT possible?
When the supply is offline.
When the motor has no brushes.
When the drive is running at constant speed.
When the system has no storage.
Explanation - Regeneration requires a path for current; an offline supply cannot accept the energy.
Correct answer is: When the supply is offline.
Q.47 Which of the following best describes the effect of regenerative braking on a vehicle's battery SOC?
SOC decreases.
SOC remains unchanged.
SOC increases.
SOC fluctuates randomly.
Explanation - Energy fed back to the battery raises its state-of-charge.
Correct answer is: SOC increases.
Q.48 What is a key benefit of combining dynamic and regenerative braking?
Higher braking torque.
Reduced heat in resistors.
Simplified control.
Lower installation cost.
Explanation - Dynamic braking handles excess torque, while regenerative reduces heat generation.
Correct answer is: Reduced heat in resistors.
Q.49 Which of the following is a major challenge in regenerative braking for electric aircraft?
Limited battery capacity.
High rotor inertia.
Noise emission.
Control complexity.
Explanation - Aircraft require precise and safe control of regenerative energy transfer.
Correct answer is: Control complexity.
Q.50 Which braking method primarily uses the magnetic field to create a resisting torque?
Dynamic braking
Regenerative braking
Electromagnetic braking
Mechanical braking
Explanation - Electromagnetic brakes rely on magnetic fields generated by currents in conductive plates.
Correct answer is: Electromagnetic braking
Q.51 The term 'brake resistor' refers to:
A mechanical component.
An electrical component.
A type of motor.
A cooling device.
Explanation - Brake resistors dissipate electrical energy as heat during dynamic braking.
Correct answer is: An electrical component.
Q.52 Which braking strategy is most suitable for a high-speed wind turbine generator?
Dynamic braking
Regenerative braking
Electromagnetic braking
Mechanical braking
Explanation - Energy recovery improves overall plant efficiency and reduces grid impact.
Correct answer is: Regenerative braking
Q.53 When a motor is in regenerative braking mode, its electrical impedance is effectively:
Low impedance.
High impedance.
Zero impedance.
Variable impedance.
Explanation - The motor behaves as a generator with high output impedance, limiting current flow.
Correct answer is: High impedance.
Q.54 Which control law is used to maintain a desired braking torque in regenerative brakes?
PID control
Fuzzy logic control
Sliding mode control
All of the above
Explanation - Various control strategies can be applied to regulate braking torque precisely.
Correct answer is: All of the above
Q.55 The main limitation of mechanical brakes in high-speed applications is:
Insufficient torque.
High wear rate.
Low reliability.
High cost.
Explanation - Mechanical brakes struggle to provide enough torque at high speeds without large pads.
Correct answer is: Insufficient torque.
Q.56 Which braking mode is most commonly employed in a CNC machine to ensure precise stopping?
Dynamic braking
Regenerative braking
Electromagnetic braking
All of the above
Explanation - CNC machines often use a combination to achieve accurate positioning and energy efficiency.
Correct answer is: All of the above
Q.57 What is the primary role of a brake controller in an industrial drive system?
Monitoring temperature.
Adjusting supply voltage.
Sequencing braking modes.
Controlling motor speed.
Explanation - The controller decides which braking method to use based on load conditions.
Correct answer is: Sequencing braking modes.
Q.58 In a regenerative braking system, the motor must be connected to:
A resistor bank.
A battery bank.
The grid only.
A capacitor bank.
Explanation - The generated current is usually stored in a battery or supercapacitor bank.
Correct answer is: A battery bank.
Q.59 Which of the following best describes the effect of dynamic braking on the motor's magnetic flux?
Flux increases.
Flux decreases.
Flux remains unchanged.
Flux oscillates.
Explanation - Dynamic braking mainly affects current and voltage, not the magnetic flux directly.
Correct answer is: Flux remains unchanged.
Q.60 The key difference between dynamic and regenerative braking is the:
Method of energy dissipation.
Motor type used.
Speed range.
Control strategy.
Explanation - Dynamic braking dissipates energy as heat; regenerative feeds it back as electrical power.
Correct answer is: Method of energy dissipation.
Q.61 In dynamic braking, the braking torque is inversely proportional to:
Speed.
Current.
Resistance.
Voltage.
Explanation - Torque ∝ speed × induced EMF, thus inversely related to speed when current is constant.
Correct answer is: Speed.
Q.62 Which braking method is most suitable for a low-power robotic arm?
Dynamic braking
Regenerative braking
Mechanical braking
Electromagnetic braking
Explanation - Low-power applications benefit from simple, reliable mechanical brakes.
Correct answer is: Mechanical braking
Q.63 Which component in a regenerative braking circuit can limit the current flowing back to the supply?
Brake resistor
Diode bridge
Capacitor bank
Inductor
Explanation - A diode bridge ensures current flows in one direction, protecting the supply.
Correct answer is: Diode bridge
Q.64 During regenerative braking, the motor’s terminal voltage is:
Negative relative to supply.
Positive relative to supply.
Zero.
Unchanged.
Explanation - The generated voltage is opposite to the supply voltage to drive current back.
Correct answer is: Negative relative to supply.
Q.65 Which of the following is a potential hazard of dynamic braking if not properly cooled?
Thermal runaway.
Short circuit.
Overvoltage.
Noise interference.
Explanation - Excess heat can lead to component failure and fire risk.
Correct answer is: Thermal runaway.
Q.66 A brake resistor must be designed to handle a maximum power of:
1 kW
10 kW
100 kW
1 MW
Explanation - Typical industrial drives may require resistors rated for several kilowatts.
Correct answer is: 10 kW
Q.67 In a regenerative braking system, the maximum recoverable power is limited by the:
Motor’s speed.
Battery’s voltage ceiling.
Resistor’s resistance.
Gear ratio.
Explanation - The battery cannot accept voltage beyond its rated maximum, capping energy recovery.
Correct answer is: Battery’s voltage ceiling.
Q.68 Which braking method is most energy efficient for a freight train operating at high speeds?
Dynamic braking only.
Regenerative braking only.
Combined regenerative and dynamic braking.
Mechanical braking only.
Explanation - Combining both maximizes energy recovery while ensuring sufficient braking torque.
Correct answer is: Combined regenerative and dynamic braking.
Q.69 In a three-phase induction motor used for regenerative braking, the phase currents:
Become zero.
Remain constant.
Become negative.
Become balanced.
Explanation - During regeneration, the currents flow in the opposite direction to normal operation.
Correct answer is: Become negative.
Q.70 Which of these is a typical control signal used to engage dynamic braking?
Brake resistor voltage.
Motor speed sensor.
Brake controller command.
Battery voltage level.
Explanation - The controller issues a command to activate the brake resistor.
Correct answer is: Brake controller command.
Q.71 Which braking method uses a 'shorted' winding to dissipate energy as heat?
Dynamic braking
Regenerative braking
Mechanical braking
Electromagnetic braking
Explanation - Shorting the winding creates high currents that generate heat.
Correct answer is: Dynamic braking
Q.72 A regenerative brake controller must monitor:
Motor speed, voltage, and current.
Only motor speed.
Only supply voltage.
Only battery temperature.
Explanation - All three parameters are needed to regulate regenerative braking safely.
Correct answer is: Motor speed, voltage, and current.
Q.73 What is the effect of adding a large inductance in the regenerative braking circuit?
Increases braking torque.
Reduces current spikes.
Increases heat generation.
Decreases system efficiency.
Explanation - Inductance smooths current changes, protecting components from surges.
Correct answer is: Reduces current spikes.
Q.74 Which braking method is used when a vehicle is stopped and the drive is disconnected from the power supply?
Dynamic braking
Regenerative braking
Mechanical braking
Electromagnetic braking
Explanation - Mechanical brakes provide reliable stopping independent of electrical power.
Correct answer is: Mechanical braking
Q.75 Which component is essential for protecting the inverter from overvoltage during regenerative braking?
Zener diode.
Flyback diode.
Snubber circuit.
All of the above.
Explanation - Each component helps clamp voltage spikes and protect electronics.
Correct answer is: All of the above.
Q.76 The braking torque produced by a mechanical brake is primarily a function of:
Brake pad material.
Motor speed.
Battery voltage.
Gear ratio.
Explanation - Friction coefficient of pads determines the torque generated.
Correct answer is: Brake pad material.
Q.77 Dynamic braking is most effective for:
Low-speed, high-torque loads.
High-speed, low-torque loads.
Constant-speed loads.
Variable-speed loads.
Explanation - At low speeds, energy can be dissipated as heat without excessive heat generation.
Correct answer is: Low-speed, high-torque loads.
Q.78 Which of the following best explains why regenerative braking is preferred in electric buses?
It eliminates the need for mechanical brakes.
It improves energy efficiency and reduces operating costs.
It increases maximum speed.
It reduces noise levels.
Explanation - Energy recovery reduces fuel consumption and extends vehicle range.
Correct answer is: It improves energy efficiency and reduces operating costs.
Q.79 What is the key factor that limits the use of regenerative braking in low-speed applications?
Insufficient back-EMF.
High braking torque.
Large motor size.
High battery voltage.
Explanation - Low speeds produce low back-EMF, reducing energy recovery capability.
Correct answer is: Insufficient back-EMF.
Q.80 Which of the following is a typical fault in a dynamic braking system?
Shorted brake resistor.
Open brake controller.
Overheating of resistors.
All of the above.
Explanation - All listed faults can impair dynamic braking performance.
Correct answer is: All of the above.
Q.81 In regenerative braking, the power converter must be capable of:
Unidirectional current flow.
Bidirectional current flow.
Only forward voltage.
Only reverse voltage.
Explanation - The converter must handle both drive and regenerative modes.
Correct answer is: Bidirectional current flow.
Q.82 Which braking mode can be used simultaneously to provide high torque and recover energy?
Dynamic braking only.
Regenerative braking only.
Combined braking.
Mechanical braking only.
Explanation - Combining methods ensures torque while also capturing energy.
Correct answer is: Combined braking.
Q.83 Which of the following is a requirement for the battery in a regenerative braking system?
High internal resistance.
Low capacity.
High voltage tolerance.
High temperature operation.
Explanation - The battery must handle the high voltage generated during braking.
Correct answer is: High voltage tolerance.
Q.84 In dynamic braking, the current through the resistor is proportional to:
Brake torque.
Motor speed.
Supply voltage.
Mechanical load.
Explanation - Higher speeds produce larger back-EMF, increasing resistor current.
Correct answer is: Motor speed.
Q.85 Which of these is a common failure mode for regenerative braking in an industrial drive?
Over-voltage across the inverter.
Under-voltage drop across the motor.
Insufficient magnetic flux.
All of the above.
Explanation - Regenerative power can exceed inverter ratings, causing damage.
Correct answer is: Over-voltage across the inverter.
Q.86 What is a key design consideration for brake resistors used in high-power drives?
Low cost.
High temperature rating.
Large physical size.
High resistance value.
Explanation - Resistors must withstand high temperatures generated during braking.
Correct answer is: High temperature rating.
Q.87 Which braking method is best suited for a 3-phase PMSM in a hybrid car?
Dynamic braking.
Regenerative braking.
Mechanical braking.
All of the above.
Explanation - PMSMs can efficiently return energy to the battery during braking.
Correct answer is: Regenerative braking.
Q.88 In an electric train, which braking system is primarily used to provide continuous braking during operation?
Dynamic braking only.
Regenerative braking only.
Electromagnetic brakes.
Mechanical brakes.
Explanation - Electromagnetic brakes offer continuous, low-maintenance braking for trains.
Correct answer is: Electromagnetic brakes.
Q.89 The primary function of a snubber circuit in a regenerative braking system is to:
Limit current spikes.
Increase braking torque.
Reduce noise.
Store energy.
Explanation - Snubbers protect switches from voltage transients during braking.
Correct answer is: Limit current spikes.
Q.90 Which of the following best describes the energy flow in dynamic braking?
Mechanical energy → Electrical energy → Heat.
Mechanical energy → Heat.
Electrical energy → Mechanical energy.
Heat → Electrical energy.
Explanation - Kinetic energy is converted to electrical energy and then dissipated as heat.
Correct answer is: Mechanical energy → Electrical energy → Heat.
Q.91 During regenerative braking, the inverter’s duty cycle is typically:
High to allow energy flow back.
Low to limit energy return.
Zero to cut off current.
Variable depending on speed.
Explanation - Duty cycle changes to control the amount of energy returned.
Correct answer is: Variable depending on speed.
Q.92 Which of the following is a benefit of using a combination of dynamic and regenerative braking in a CNC machine?
Reduced power consumption.
Higher braking torque.
Simpler control logic.
Lower system cost.
Explanation - Combining methods recovers energy and reduces heat, saving power.
Correct answer is: Reduced power consumption.
Q.93 Which parameter is NOT affected by regenerative braking in an electric motor?
Rotor temperature.
Terminal voltage.
Supply voltage.
Motor speed.
Explanation - Regenerative braking reduces speed; it's a direct effect, not an unaffected parameter.
Correct answer is: Motor speed.
Q.94 Which of these is a typical failure mode for the brake resistor in a dynamic braking circuit?
Thermal runaway leading to melting.
Short circuit due to metal contacts.
Oxidation of contacts.
All of the above.
Explanation - All listed failures can compromise the resistor’s performance.
Correct answer is: All of the above.
Q.95 Which braking method can be used when the power supply is not available?
Dynamic braking.
Regenerative braking.
Mechanical braking.
All of the above.
Explanation - Mechanical brakes do not rely on external power.
Correct answer is: Mechanical braking.
Q.96 Which of the following best describes the energy conversion process in regenerative braking?
Kinetic → Electrical → Chemical.
Electrical → Mechanical → Chemical.
Mechanical → Chemical → Electrical.
Mechanical → Electrical → Chemical.
Explanation - Kinetic energy is converted to electrical power which is stored chemically in batteries.
Correct answer is: Mechanical → Electrical → Chemical.
Q.97 What is the main safety function of an overvoltage protection relay in a regenerative braking system?
To limit current.
To limit voltage.
To limit temperature.
To limit speed.
Explanation - The relay disconnects the circuit if voltage exceeds safe limits.
Correct answer is: To limit voltage.
Q.98 Which of the following is a major drawback of regenerative braking at very high speeds?
Insufficient torque.
Excessive heat in resistors.
Inability to return energy.
High mechanical wear.
Explanation - At very high speeds, the power electronics may not be able to handle the high currents.
Correct answer is: Inability to return energy.
Q.99 Which of the following best describes a hybrid braking system?
A system that uses only dynamic braking.
A system that uses only regenerative braking.
A system that uses both dynamic and regenerative braking.
A system that uses only mechanical braking.
Explanation - Hybrid braking blends both methods for optimal performance.
Correct answer is: A system that uses both dynamic and regenerative braking.
Q.100 Which braking mode is typically engaged when an electric vehicle stops in a low-speed parking scenario?
Dynamic braking.
Regenerative braking.
Mechanical braking.
Electromagnetic braking.
Explanation - At low speeds, regenerative braking is ineffective; mechanical brakes provide stopping power.
Correct answer is: Mechanical braking.
Q.101 What is a common method for controlling the transition between dynamic and regenerative braking?
Using a voltage divider.
Using a current sense resistor.
Using a PWM controller.
Using a mechanical switch.
Explanation - PWM allows precise control of braking modes.
Correct answer is: Using a PWM controller.
Q.102 Which braking method is most energy efficient when the drive is connected to the grid?
Dynamic braking.
Regenerative braking.
Mechanical braking.
All of the above.
Explanation - Energy can be returned to the grid, increasing overall efficiency.
Correct answer is: Regenerative braking.
Q.103 Which of these is a typical parameter measured by a brake controller for dynamic braking?
Motor speed.
Motor temperature.
Battery voltage.
All of the above.
Explanation - Motor speed determines the braking torque in dynamic braking.
Correct answer is: Motor speed.
Q.104 In regenerative braking, the power converter must have:
High bandwidth.
Low bandwidth.
Fixed frequency.
No voltage rating.
Explanation - High bandwidth allows quick response to changes in braking conditions.
Correct answer is: High bandwidth.
Q.105 What is the main limitation of dynamic braking for high-power drives?
High heat generation.
Low braking torque.
Complex control.
High cost.
Explanation - Large power dissipation in resistors makes it impractical for high-power drives.
Correct answer is: High heat generation.
Q.106 Which of the following is a typical application of regenerative braking?
Electric cars.
Wind turbines.
Elevators.
All of the above.
Explanation - Regenerative braking is used in various electrically driven systems.
Correct answer is: All of the above.
Q.107 Which braking method is most effective in a 4‑wheel electric car for reducing brake wear?
Dynamic braking.
Regenerative braking.
Mechanical braking.
All of the above.
Explanation - Regenerative braking reduces reliance on mechanical brakes, thus reducing wear.
Correct answer is: Regenerative braking.
Q.108 Which of the following is NOT typically used to protect a regenerative braking system?
Fuses.
Thermistors.
Cooling fans.
Mechanical springs.
Explanation - Mechanical springs are not used for electrical protection.
Correct answer is: Mechanical springs.
Q.109 In regenerative braking, the electrical energy generated is primarily converted to:
Mechanical energy.
Heat energy.
Chemical energy in the battery.
Sound energy.
Explanation - Energy is stored chemically in the battery for future use.
Correct answer is: Chemical energy in the battery.
Q.110 Which type of motor is most suitable for regenerative braking in an industrial drive?
DC brushed motor.
Induction motor.
Universal motor.
Brushless DC motor.
Explanation - BLDC motors have high efficiency and controllability for regeneration.
Correct answer is: Brushless DC motor.
Q.111 Which of the following statements about dynamic braking is FALSE?
It requires a resistor to dissipate energy.
It can provide high torque at low speeds.
It recovers energy back to the battery.
It can be activated by a controller.
Explanation - Dynamic braking dissipates energy as heat, not recover it.
Correct answer is: It recovers energy back to the battery.
Q.112 Which braking method uses the magnetic field of the rotor to create a resisting force without electrical energy conversion?
Dynamic braking.
Regenerative braking.
Electromagnetic braking.
Mechanical braking.
Explanation - Electromagnetic brakes use eddy currents to create a magnetic opposing force.
Correct answer is: Electromagnetic braking.
Q.113 What is the primary role of the brake resistor in a dynamic braking circuit?
To store energy.
To generate magnetic flux.
To dissipate heat.
To increase voltage.
Explanation - The resistor converts electrical energy into heat during braking.
Correct answer is: To dissipate heat.
Q.114 Which of the following is a major advantage of regenerative braking over dynamic braking?
Higher mechanical wear.
Simplicity.
Energy recovery.
Lower cost.
Explanation - Regenerative braking captures energy rather than wasting it as heat.
Correct answer is: Energy recovery.
Q.115 Which braking method is typically used in electric elevators?
Dynamic braking.
Regenerative braking.
Electromagnetic braking.
Mechanical braking.
Explanation - Electromagnetic brakes are reliable and require minimal maintenance for elevators.
Correct answer is: Electromagnetic braking.
Q.116 Which of the following is a requirement for a resistor used in a dynamic braking system?
High resistance value.
Low resistance value.
Low power rating.
High power rating.
Explanation - Brake resistors must handle high power dissipation during braking.
Correct answer is: High power rating.
Q.117 What is a typical control method for ensuring smooth braking transitions in an electric drive?
PID control.
Fuzzy logic.
Open-loop.
All of the above.
Explanation - Various control strategies can be employed depending on the system requirements.
Correct answer is: All of the above.
Q.118 In a regenerative braking system, the inverter must have a high-current rating to handle:
The braking current.
The supply current.
The motor current.
The battery current.
Explanation - During braking, the current can be substantial and must be safely handled.
Correct answer is: The braking current.
Q.119 Which of the following braking modes is most suitable for a high-speed freight train that requires energy recovery?
Dynamic braking.
Regenerative braking.
Electromagnetic braking.
Mechanical braking.
Explanation - Energy recovery at high speeds is critical for freight train efficiency.
Correct answer is: Regenerative braking.
Q.120 Which component is essential for protecting the motor during regenerative braking?
Brake resistor.
Current sensor.
Voltage clamp.
All of the above.
Explanation - Each component helps manage current, voltage, and heat during braking.
Correct answer is: All of the above.
Q.121 What is the key factor limiting the amount of energy that can be recovered in regenerative braking?
Motor speed.
Battery voltage.
Brake resistor value.
Gear ratio.
Explanation - The battery's voltage ceiling limits how much current can be absorbed.
Correct answer is: Battery voltage.
Q.122 Which braking method is used when the motor must be stopped quickly in an electric conveyor belt?
Dynamic braking.
Regenerative braking.
Mechanical braking.
All of the above.
Explanation - A combination ensures quick stopping and energy recovery.
Correct answer is: All of the above.
Q.123 Which of the following is NOT a typical control parameter for regenerative braking?
Brake torque setpoint.
Current limit.
Voltage limit.
Rotor temperature.
Explanation - Regenerative braking control focuses on current, voltage, and torque, not temperature directly.
Correct answer is: Rotor temperature.
Q.124 Which type of braking system is commonly used in electric cars for parking brakes?
Dynamic braking.
Regenerative braking.
Mechanical brake.
Electromagnetic brake.
Explanation - Parking requires a fail-safe mechanical system independent of electrical power.
Correct answer is: Mechanical brake.
Q.125 During regenerative braking, the inverter typically uses:
Single-phase PWM.
Three-phase PWM.
Half-bridge DC-DC.
Half-bridge inverter.
Explanation - Three-phase PWM controls the inverter for efficient energy return.
Correct answer is: Three-phase PWM.
Q.126 What is the primary function of a brake controller in a hybrid vehicle?
To control engine speed.
To control regenerative braking.
To control battery temperature.
To control tire pressure.
Explanation - The controller manages how much energy is recovered during braking.
Correct answer is: To control regenerative braking.
Q.127 Which braking method can cause a sudden drop in voltage at the motor terminals during engagement?
Dynamic braking.
Regenerative braking.
Mechanical braking.
Electromagnetic braking.
Explanation - Dynamic braking short-circuits the windings, dropping terminal voltage.
Correct answer is: Dynamic braking.
Q.128 Which of the following is a common failure mode for a regenerative braking system?
Over-voltage across the inverter.
Under-voltage across the motor.
Open-circuit in the brake resistor.
All of the above.
Explanation - Each fault can compromise the system’s operation.
Correct answer is: All of the above.
Q.129 The energy recovered during regenerative braking is stored in the:
Capacitor bank.
Flywheel.
Battery.
All of the above.
Explanation - In most systems, the recovered energy is stored chemically in a battery.
Correct answer is: Battery.
Q.130 Which braking method is used in high-speed trains for continuous braking while also recovering energy?
Dynamic braking.
Regenerative braking.
Electromagnetic braking.
All of the above.
Explanation - Trains use a mix of regenerative and electromagnetic braking for efficiency.
Correct answer is: All of the above.
Q.131 In regenerative braking, the power electronics must handle:
High current.
Low voltage.
Constant frequency.
Low bandwidth.
Explanation - The system must be capable of handling large currents during energy recovery.
Correct answer is: High current.
Q.132 Which of the following braking modes provides the highest braking torque at low speeds?
Dynamic braking.
Regenerative braking.
Electromagnetic braking.
Mechanical braking.
Explanation - Mechanical brakes can deliver high torque regardless of speed.
Correct answer is: Mechanical braking.
Q.133 In a regenerative braking system, the inverter’s duty cycle is primarily controlled by:
Speed sensor.
Voltage sensor.
Current sensor.
All of the above.
Explanation - All sensors contribute to determining the correct duty cycle.
Correct answer is: All of the above.
Q.134 Which braking method is best suited for a high-power industrial motor that requires frequent stops?
Dynamic braking.
Regenerative braking.
Mechanical braking.
All of the above.
Explanation - A combination provides both quick stopping and energy efficiency.
Correct answer is: All of the above.
Q.135 What is the primary advantage of mechanical brakes in a hybrid electric vehicle?
Energy recovery.
Low cost.
Redundancy and fail-safe operation.
High speed operation.
Explanation - Mechanical brakes provide a reliable backup when electrical systems fail.
Correct answer is: Redundancy and fail-safe operation.
Q.136 Which of the following statements about regenerative braking is TRUE?
It dissipates energy as heat.
It requires a resistor bank.
It returns energy to the battery or grid.
It cannot be used in high-speed applications.
Explanation - Regenerative braking captures kinetic energy for storage.
Correct answer is: It returns energy to the battery or grid.
Q.137 Which braking method is used in most electric scooters for efficient braking?
Dynamic braking.
Regenerative braking.
Mechanical braking.
Electromagnetic braking.
Explanation - Scooters often use regenerative braking to recharge the battery during braking.
Correct answer is: Regenerative braking.
Q.138 Which of the following is a typical component of a regenerative braking system?
Brake resistor.
Motor windings.
Inverter.
All of the above.
Explanation - All components interact in a regenerative braking system.
Correct answer is: All of the above.
Q.139 Which braking method is most suitable for an industrial conveyor system that operates at constant speed?
Dynamic braking.
Regenerative braking.
Mechanical braking.
Electromagnetic braking.
Explanation - At constant speed, regenerative braking offers little benefit.
Correct answer is: Mechanical braking.
Q.140 Which of the following is the primary function of a brake controller during braking?
Measure motor speed.
Control braking torque.
Measure battery voltage.
All of the above.
Explanation - The controller adjusts the torque applied during braking.
Correct answer is: Control braking torque.
Q.141 Which braking method uses the motor's inherent electrical resistance to slow down the drive?
Dynamic braking.
Regenerative braking.
Mechanical braking.
Electromagnetic braking.
Explanation - Dynamic braking relies on the motor acting as a generator with its resistance.
Correct answer is: Dynamic braking.
Q.142 In regenerative braking, the motor generates a voltage that is:
Lower than the supply voltage.
Higher than the supply voltage.
Equal to the supply voltage.
Zero.
Explanation - During braking, the induced voltage exceeds the supply voltage.
Correct answer is: Higher than the supply voltage.
Q.143 Which of the following is a major consideration when selecting a brake resistor for dynamic braking?
Power rating.
Mechanical strength.
Weight.
Color.
Explanation - The resistor must handle the expected braking power.
Correct answer is: Power rating.
Q.144 Which braking method can be used to slow an electric motor while also feeding energy back to the power grid?
Dynamic braking.
Regenerative braking.
Mechanical braking.
All of the above.
Explanation - Regenerative braking captures energy that can be returned to the grid.
Correct answer is: Regenerative braking.
Q.145 Which of the following is NOT a type of braking method used in electric drives?
Dynamic braking
Regenerative braking
Eddy current braking
Sine wave braking
Explanation - Sine wave braking is not a recognized braking technique.
Correct answer is: Sine wave braking
Q.146 In a regenerative braking system, what happens to the motor’s back EMF during braking?
It decreases.
It remains constant.
It increases.
It disappears.
Explanation - Back EMF rises as the motor decelerates, driving current back into the grid.
Correct answer is: It increases.
Q.147 Which braking mode is most suitable for a high-speed wind turbine generator to recover energy during cut-off?
Dynamic braking.
Regenerative braking.
Electromagnetic braking.
Mechanical braking.
Explanation - Energy recovery at high speeds improves overall plant efficiency.
Correct answer is: Regenerative braking.
Q.148 Which of the following is a typical application of dynamic braking?
Electric trains during long descents.
Electric cars in urban driving.
Wind turbines during grid outages.
All of the above.
Explanation - Dynamic braking is used for energy dissipation where recovery is not possible.
Correct answer is: Electric trains during long descents.
Q.149 What is the primary advantage of using regenerative braking in an electric vehicle?
Increased acceleration.
Reduced braking noise.
Reduced energy consumption.
Simplified control.
Explanation - Regenerative braking recovers energy, improving range and efficiency.
Correct answer is: Reduced energy consumption.
Q.150 Which of the following best describes the energy conversion in regenerative braking?
Kinetic energy → Electrical energy → Thermal energy.
Mechanical energy → Electrical energy → Chemical energy.
Electrical energy → Mechanical energy → Chemical energy.
Electrical energy → Thermal energy → Mechanical energy.
Explanation - The energy is captured as electrical power and stored chemically in a battery.
Correct answer is: Mechanical energy → Electrical energy → Chemical energy.
Q.151 Which braking method is most effective for a high-speed electric locomotive that needs to recover energy?
Dynamic braking.
Regenerative braking.
Electromagnetic braking.
Mechanical braking.
Explanation - Regenerative braking recovers energy for the locomotive’s battery or the grid.
Correct answer is: Regenerative braking.
Q.152 Which of the following is a typical feature of a regenerative braking controller?
Voltage monitoring.
Current limiting.
Speed measurement.
All of the above.
Explanation - All these parameters are monitored to regulate braking safely.
Correct answer is: All of the above.
Q.153 What is the key benefit of a hybrid braking system in an industrial drive?
Higher braking torque.
Energy recovery and reduced heat.
Lower component count.
Simpler maintenance.
Explanation - A hybrid system recovers energy and limits heat generation, improving performance.
Correct answer is: Energy recovery and reduced heat.